Sedative, cardiovascular, haematologic and biochemical effects of four different drug combinations administered intramuscularly in cats.

Objective: To compare effects of four drug combinations on sedation, echocardiographic, haematologic and biochemical variables and recovery in cats.
Study Design: Experimental randomized 'blinded' cross-over study.
Animals: Six healthy cats.
Materials and Methods: Treatments were administered intramuscularly: midazolam 0.4 mg kg(-1) and butorphanol 0.4 mg kg(-1) (MB); midazolam 0.4 mg kg(-1), butorphanol 0.4 mg kg(-1) and ketamine 3 mg kg(-1) (MBK); midazolam 0.4 mg kg(-1), butorphanol 0.4 mg kg(-1) and dexmedetomidine 5 μg kg(-1) (MBD); ketamine 3 mg kg(-1) and dexmedetomidine 5 μg kg(-1) (KD). Sedation was evaluated at time-points over 10 minutes post injection. Echocardiography, systolic arterial blood pressure (SAP) measurement and blood sampling were performed at baseline and from 10 minutes after treatment. Quality of recovery was scored. Data were analysed by anova for repeated measures. p < 0.05 was considered significant.
Results: The lowest sedation score was obtained by MB, (median 10.5 [7; 20]), highest by KD (36.5 [32; 38]). Quality of recovery was best with KD (0.5 [0; 2]), and worst with MB (7.5 [4; 11]). Relative to baseline measurements, treatments decreased SAP by 17%, 25%, 13%, 5% in MB, MBK, MBD and KD, respectively. Heart rate decreased (p < 0.05) after MBD (44%) and KD (34%). All treatments decreased stroke volume by 24%, 21%, 24%, 36%, and cardiac output by 23%, 34%, 54%, 53% in MB, MBK, MBD and KD, respectively. Packed cell volume was decreased (p < 0.05) by 20%, 31%, 29% in MBK, MBD and KD, respectively. Plasma glucose was increased after MBD (31%) and KD (52%) and lactate concentration was decreased (p < 0.05) after MBK (58%), MBD (72%) and KD (65%).
Conclusions and Clinical Relevance: The MB combination did not produce sedation in healthy cats. Treatment MBK led to acceptable sedation and minimal cardiovascular changes. Both treatments with dexmedetomidine produced excellent sedation and recovery but induced more cardiovascular depression and haematologic changes.
(© 2012 The Authors. Veterinary Anaesthesia and Analgesia. © 2012 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.)